you can get a mesh that will stop the butterflies geting through, and it will also stop the bees that you need to polinate the fruit, and the ladybirds that eat the greenfly, there is a an old fashoned remarde for cabage whites that I finde has allways worked for me, place a small jam jar in the ground with just about an inch exposed under the plants about every 2to 3 feet apart and half fill with parifin, still check under the leaves for eggs , but you will not finde meny.and what ever netting you use and it dose not need to be small mesh make shore that it is well pined down without the smallest gap, because the blackbirds love a chalange.

You don't need to pollinate the flowers on soft fruit, the wind will do that and you are not growing fruit for seeds. The main thing to remember is snow at this time of year, it will break down the whole fruit cage, even metal uprights. As Cliffo says watch out for Blackbirds. Low wire netting at the base is best, easy to keep weed free.

I have a fruit cage and the netting is about 1/2" square and i was amazed when butterflies still got through. I plant nasturtiums next to the cabbages and more eggs get laid on the nasts than on the cabbages.

thnaks every one for advice